Heavy equipment, such as bulldozers, load-haul-dump machines (LHDs), wheel loaders, carry dozers, etc., are used during an excavation process and when moving overburden material from an area of a job site in order to expose a material that is being mined. An earthmoving machine may scoop up material from a first location and push a pile of the material loaded into and in front of a work implement of the machine, such as a dozer blade, to a second location where the pile contacts another pile of dirt in front of it. Successive piles of dirt are placed behind each other in a method referred to as backstacking the piles. The backstacking of the piles of dirt may be performed in a pivot push operation when the material being moved is not pushed over a crest. In a pivot push operation the earthmoving machine cuts into surface material for a period of time to load the work implement with the material, and then stops cutting and moves the material to a side of the cast or slot that the machine is forming. The piles of material moved to the side may be backstacked, smoothed over, and then additional piles may be backstacked on top of the layer formed by backstacked piles. The intent of backstacked piles is to build layers of dirt by placing individual piles in a row, starting from a low wall, and moving forward to the pivot point. The piles are then smoothed over and compacted by the machine when it drives up on the piles to start a new layer. A productivity of the excavation process can be affected by an efficiency of each machine during every excavation cycle. In particular, the efficiency of each machine increases when the machine's work implement (e.g., a straight or curved dozer blade) is fully loaded with material within a short amount of time, and the resulting pile of dirt is placed adjacent to a previous pile of dirt at the correct shape and spacing to prevent sloughing of the material and to allow for efficient smoothing of the piles in each layer. The preferred pile spacing and machine characteristics change dynamically depending on the pitch of the machine and surrounding terrain when attempting the backstacking of the piles.
Some applications require operation of the heavy equipment under hazardous working conditions. In these applications, some or all of the machines can be remotely or autonomously controlled to complete the excavation process. When a machine is remotely or autonomously controlled, however, situational awareness may be limited. That is, it can be difficult for the remote operator or the automated system to accurately determine a degree of tool engagement with the pile during the loading segment of the excavation process. As a result, the machine's tool may be underloaded during a particular loading segment, or overloaded, where too much energy and time may be consumed by attempting to increase loading of the tool.
One attempt to improve efficiency in the loading segment of the excavation process is disclosed in U.S. Pat. No. 8,363,210 of Montgomery that issued on Jan. 29, 2013 (“the '210 patent”). Specifically, the '210 patent discloses a system for locating a topographic feature at a job-site. The system includes a laser range finder connected to the arm of an excavator, and a computer in communication with the laser range finder. The laser range finder directs a pattern of light onto the topographic feature, and the computer is configured to receive a reflection of the light, thereby locating a point on the feature. By directing the light onto multiple different points of the feature, the computer may, through the use of common equations, be able to determine a location, angle, slope, grade, and volume of the feature.
Although the system of the '210 patent may provide information that could possibly improve machine efficiencies, the system may still be less than optimal. In particular, the system may require the excavator to be stationary; the location of the excavator may need to be precisely known; movements of the excavator may need to be accurately tracked; and the light may need to be manually and perfectly aimed. In addition, in order to determine feature parameters other than a single point location, the system may have to separately detect the locations of multiple different points so that the corresponding calculations can be performed. These actions may take a significant amount of time, and also allow for the introduction of error.
The disclosed autonomous method for controlling an earthmoving machine is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.